• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.2
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• pp.1-6
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• 2016

A ground air heat exchanger (GAHX), also called earth air heat exchanger is a useful technology to be integrated with other renewable energy technologies. In this study, ground-air heat exchanger system for the air source heat pump is introduced. The purpose of this study is to design the volumetric flow rate and the length of GAHX system. A GAHX length model equation has been developed and used for calculation. GAHX thermal efficiency are recommended as 75% and 85% in order to optimize pipe length. $2,750m^3/h$, $2,420m^3/h$ of volumetric flow rate on 88.3m, 111.7m length are suggested for providing 7.5kW thermal capacity. And the number of path is recommended more than two to minimize pressure drop. For future study, advanced model equation study with ground thermal behavior and a more efficient GAHX design will be considered.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.59-74
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• 2009

Relative navigation system is presented using GPS measurements from a single-channel global positioning system (GPS) simulator. The objective of this study is to provide the real-time inter-satellite relative positions as well as absolute positions for two formation flying satellites in low earth orbit. To improve the navigation performance, the absolute states are estimated using ion-free GRAPHIC (group and phase ionospheric correction) pseudo-ranges and the relative states are determined using double differential carrier-phase data and singled-differential C/A code data based on the extended Kalman filter and the unscented Kalman filter. Furthermore, pseudo-relative dynamic model and modified relative measurement model are developed. This modified EKF method prevents non-linearity of the measurement model from degrading precision by applying linearization about absolute navigation solutions not about the priori estimates. The LAMBDA method also has been used to improve the relative navigation performance by fixing ambiguities to integers for precise relative navigation. The software-based simulation has been performed and the steady state accuracies of 1 m and 6 mm ($1{\sigma}$ of 3-dimensional difference errors) are achieved for the absolute and relative navigation using EKF for a short baseline leader/follower formation. In addition, the navigation performances are compared for the EKF and the UKF for 10 hours simulation, and relative position errors are mm-level for the two filters showing the similar trends.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.79-87
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• 2009

International Standard Organization for Standardization Technical Committee 211(ISO TC 211) aims to define and develop standards for information concerning objects or phenomena that are directly or indirectly associated with a location relative to the Earth. ISO TC 211 is working with LADM as a new project based on the existing research which is CCDM. Land Administration Domain Model is, as a international standard model, mainly connected to administration law, spatial surveying components related to cadastre all over the world and provides an extensive basis for an efficient and effective land administration system to avoid reinvention and re-implemention. Further, LADM helps to communicate land information both within a country and between different countries. This study introduces what LADM is and researches how to adopt administration law, spatial surveying components of LADM for Korea Land Information System(KLIS).

• Journal of the Korean Institute of Landscape Architecture
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• v.23 no.1
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• pp.95-109
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• 1995

All human spatial behavior and psychological stress are affected by the 'Privacy'of each space. This Paper deals with the theoretical review of 'privacy'concept and establishment of 'Privacy Model' that can be a useful design tool. 'Privacy Index(Pl)' model of 10 point scale, which is based on 'Hierarchic system of Privacy' in urban spaces by Chermeyeff and Alexander(1963), was established as a hypothetical model in this study. And'Activity Suitability', based on each hierarchy of primacy level, was investigated at each site to construct the validity of 'Privacy Model'. Total 67 sites were investigated by on.-site questionnaire in 3 types of outdoor spaces, (Park), (Campus), and (Garden) respectively. The major results are as follows; 1. The P7rivacy level of earth spaces, distributed from to in and . and (Groun Private> spaces are dominant In , spaces are dondnant 2, Privacy level, based on , showed higher privacy level than that of . This means the criteria of each privacy level should be modified for more specific space. The . could be derived from the (Activity Suitability) of each space. 3.The cognition of privacy level. by user group, showed no significant difference in dach group by sex, age, education, and job, respectively.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.507-514
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• 2013

Recent reports about Mt. Baekdusan indicate an increasing potential of lahar generation due to volcanic activity around Lake Cheonji. In this study, we model lahar assuming volcanic activity underneath the caldera located at the top of Mt. Baekdusan. Lahar-inundation hazard zones (LAHARZ), software that runs within a Geographic Information System (GIS), was used for lahar modeling in various conditions of digital terrain resolution and model parameters. The sensitivity analysis of model parameters shows that both sink threshold and terrain resolution have limited impact on the modeling result. Combinations of stream threshold and resolution indicate distinctive distributions in stream delineation. The limitations of LAHARZ seem to largely be associated with the assumption of an existing flow generation algorithm. However, the impact of different resolutions on the final lahar extent was found to be small.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.451-460
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• 2006

Since low earth orbit (LEO) satellite constellations have important advantages over geosynchronous earth orbit (GEO) systems such as low propagation delay, low power requirements, and more efficient spectrum allocation due to frequency reuse between satellites and spotbeams, they are considered to be used to complement the existing terrestrial fixed and wireless networks in the evolving global mobile network. However, one of the major problems with LEO satellites is their higher speed relative to the terrestrial mobile terminals, which move at lower speeds but at more random directions. Therefore, handover management in LEO satellite networks becomes a very challenging task for supporting global mobile communication. Efficient and accurate methods are needed for LEO satellite handovers between the moving footprints. In this paper, we propose a new seamless handover management scheme for LEO satellites (SeaHO-LEO), which utilizes the handover management schemes aiming at decreasing latency, data loss, and handover blocking probability. We also present another interesting handover management model called satellite mobility pattern based handover management in LEO satellites (PatHO-LEO) which takes mobility pattern of both satellites and mobile terminals into account to minimize the handover messaging traffic. This is achieved by the newly introduced billboard manager which is used for location updates of mobile users and satellites. The billboard manager makes the proposed handover model much more flexible and easier than the current solutions, since it is a central server and supports the management of the whole system. To show the performance of the proposed algorithms, we run an extensive set of simulations both for the proposed algorithms and well known handover management methods as a baseline model. The simulation results show that the proposed algorithms are very promising for seamless handover in LEO satellites.

• Korean Journal of Remote Sensing
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• v.26 no.6
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• pp.653-664
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• 2010

The land surface reflectance is a key parameter influencing the climate near the surface. Therefore, it must be determined with sufficient accuracy for climate change research. In particular, the characteristics of the bidirectional reflectance distribution function (BRDF) when using earth observation system (EOS) are important for normalizing the reflected solar radiation from the earth's surface. Also, wide swath satellites like SPOT/VGT (VEGETATION) permit sufficient angular sampling, but high resolution satellites are impossible to obtain sufficient angular sampling over a pixel during short period because of their narrow swath scanning. This gives a difficulty to BRDF model based reflectance normalization of high resolution satellites. The principal objective of the study is to add BRDF modeling of high resolution satellites and to supply insufficient angular sampling through identifying BRDF components from SPOT/VGT. This study is performed as the preliminary data for apply to high-resolution satellite. The study provides surface parameters by eliminating BRD effect when calculated biophysical index of plant by BRDF model. We use semi-empirical BRDF model to identify the BRD components. This study uses SPOT/VGT satellite data acquired in the S1 (daily) data. Modeled reflectance values show a good agreement with measured reflectance values from SPOT satellite. This study analyzes BRD effect components by using the NDVI(Normalized Difference Vegetation Index) and the angle components such as solar zenith angle, satellite zenith angle and relative azimuth angle. Geometric scattering kernel mainly depends on the azimuth angle variation and volumetric scattering kernel is less dependent on the azimuth angle variation. Also, forest from land cover shows the wider distribution of value than cropland, overall tendency is similar. Forest shows relatively larger value of geometric term ($K_1{\cdot}f_1$) than cropland, When performed comparison between cropland and forest. Angle and NDVI value are closely related.

• Atmosphere
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• v.28 no.4
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• pp.403-414
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• 2018

Predictability of Northern Hemisphere blocking in the Korea Meteorological Administration (KMA) Global Data Assimilation and Prediction System (GDAPS) is evaluated for the period of July 2016 to May 2017. Using the operational model output, blocking is defined by a meridional gradient reversal of 500-hPa geopotential height as Tibaldi-Molteni Index. Its predictability is quantified by computing the critical success index and bias score against ERA-Interim data. It turns out that Northwest Pacific blockings, among others, are reasonably well predicted with a forecast lead time of 2~3 days. The highest prediction skill is found in spring with 3.5 lead days, whereas the lowest prediction skill is observed in autumn with 2.25 lead days. Although further analyses are needed with longer dataset, this result suggests that Northern Hemisphere blocking is not well predicted in the operational weather prediction model beyond a short-term weather prediction limit. In the spring, summer, and autumn periods, there was a tendency to overestimate the Western North Pacific blocking.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.72-77
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• 2012

There are insufficient models that find problems and solutions for accident prevention through risk assessment and suggest safe work process and work instruction from foundation works to finish work for accident decrease. This paper presents a quantitative risk assessment model by analysis of risk factors in each process such as earth works, drainage works, pavement works, appurtenant works and etc based on accident examples and investigation on actual condition in roads construction work. In addition, the safety management system was developed to perform risk assessment of construction and use it for effective safety training for labor.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.669-675
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• 2003

This paper examines structural breaks and asymmetries of prices of four domestic petroleum products, i.e., gasoline, kerosene, diesel, and bunker-C, following the changes in the pricing policies pertaining to petroleum products in Korea from the government-controlled pricing system to the market pricing system. We use the monthly wholesale market price data for the sample period between July 1988 and December 2001. Using the four methods: the Chow test, the CUSUM/CUSUMQ tests, the Bayesian approach and the Dufour test, the structural behaviors of the petroleum product prices are examined. We found that structural change occurred in all petroleum products, with the exception of Kerosene, at the point of pricing policy change from government-controlled to the spot-price related pricing system. We, also conducted asymmetric analysis using the Borenstein, Cameron, and Gilbert (1997)'s model and found evidences of price asymmetry for all four product types, but in different pattern for each product.